Spiders that decorate their webs at higher frequency intercept more prey and grow faster

Abstract

Many orb-weaving spiders decorate their webs with extra, bright white, ultraviolet light reflecting silk. Previous studies suggest that these decorations increase a spider's foraging efficiency by improving web attractiveness, which is known as the prey-attraction hypothesis. One assumption of this hypothesis is that individuals which decorate their webs at a higher frequency are expected to have a higher growth rate. Using a decoration-building orb-weaving spider, Argiope versicolor, I show a strong positive relationship between the growth rate in terms of weight gain and the frequency of decoration-building, as well as the rate of insect interception. This is the first study to reveal a fitness consequence of decorating behaviour in spiders.

Figure 1

A spider-eating jumping spider P. labiata feeding on a juvenile A. versicolor on a web with a discoid decoration. Scale bar, 1 cm.

Figure 2

Scatterplot matrix of the weight gain (Y) of A. versicolor juveniles (n=52) in a 6 day period by the initial weight (X₁), the frequency (X₂) of decoration-building (number of days in which A. versicolor built a web with a stabilimentum in a 6 day period) and the rate (X₃) of insect interception (IICR; average number of insects trapped per web per 6 h trial) of webs built by A. versicolor juveniles (n=52; Y=0.616+0.126X₁+0.001X₂+0.002X₃; p<0.001, r²=0.414).

Figure 3

Number of insects intercepted by webs with or without discoid decorations built by A. versicolor juveniles. Medians (line within the box), quartiles (box), 90th percentiles (whiskers) and extreme points (circles) are shown.